Osmotic dosage systems comprising means for delivering a solid drug formulation by displacing physically the solid drug formulation from the osmotic system are known to the prior art in U.S. Pat. No. 4,327,725 issued to Cortese and Theeuwes, and in U.S. Pat. Nos. 4,612,008; 4,765,989; and 4,783,337 issued to Wong, Barclay, Deters and Theeuwes. An osmotic system comprising means for displacing physically a liquid drug formulation from an osmotic system is known to the prior art in U.S. Pat. No. 4,627,850 issued to Deters, Theeuwes, Mullins and Eckenhoff.
The osmotic systems disclosed in these patents mentioned immediately above comprise in at least a part a semipermeable wall that surrounds a compartment. The compartment comprises a drug formulation, and in contact with the drug formulation, a displacement member that pushes the drug formulation from the osmotic system. These osmotic systems operate by imbibing fluid through the semipermeable wall into the compartment, wherein the fluid contacts and motivates the displacement member to consume space and thereby pushes the drug formulation from the osmotic system. These osmotic systems operate successfully for their intended use, and they can deliver many difficult to deliver drugs for their intended purpose. One limitation, however, associated with these osmotic systems consist in the drug formulation being in direct contact with the displacement member as it may be incompatible therewith, while another limitation is that the osmotic system imbibes into the compartment fluid that may be incompatible with the drug formulation.
It will be appreciated, in the light of the above presentation, by those versed in the drug delivery art, that if an osmotic system can be provided that overcomes the limitations associated with the prior art, and exhibits a high level of drug delivery activity, such an osmotic system would have a positive therapeutic value and represent an advancement in the dispensing art. Likewise, it will be immediately appreciated by those versed in dispensing art that if an osmotic system is made available for delivering a liquid drug formulation at a controlled and pharmodynamic osmotic activity, said osmotic system would find practical applications in the fields of pharmacy, human medicine and veterinary medicine.